TreeView.TreeNodeCheckChanged Event
Occurs when a check box in the TreeView control changes state between posts to the server.
Assembly: System.Web (in System.Web.dll)
The TreeNodeCheckChanged event is raised when a check box in the TreeView control changes state between posts to the server. This allows you to provide an event-handling method that performs a custom routine, such as updating a database or the displayed content, whenever this event occurs.
Even though the TreeNodeCheckChanged event is fired on post back, changing a check box does not cause a post back.
For more information about handling events, see NIB: Consuming Events.
The following code example demonstrates how to use the TreeNodeCheckChanged event to update a Label control when the check boxes of the TreeView control change state between posts to the server.
<%@ Page Language="VB" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <script runat="server"> Sub LinksTreeView_CheckChanged(ByVal sender As Object, ByVal e As TreeNodeEventArgs) If LinksTreeView.CheckedNodes.Count > 0 Then ' Clear the message label. Message.Text = "You selected: <br /><br />" ' Iterate through the CheckedNodes collection and display ' the selected nodes. Dim node As TreeNode For Each node In LinksTreeView.CheckedNodes Message.Text &= node.Text & "<br />" Next Else Message.Text = "No items selected." End If End Sub </script> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> <title>TreeView CheckChanged Example</title> </head> <body> <form id="form1" runat="server"> <h3>TreeView CheckChanged Example</h3> <!-- Set the ShowCheckBoxes property declaratively. --> <!-- Because the ShowCheckBoxes property uses a flag --> <!-- enumeration, you can combine multiple values by --> <!-- using the bitwise OR operator. In declarative --> <!-- syntax, this is done using a comma separated --> <!-- list. --> <asp:TreeView id="LinksTreeView" ForeColor="Blue" ExpandDepth="2" ShowCheckBoxes="Parent,Leaf" OnTreeNodeCheckChanged="LinksTreeView_CheckChanged" runat="server"> <LevelStyles> <asp:TreeNodeStyle ChildNodesPadding="10" Font-Bold="true" Font-Size="12pt" ForeColor="DarkGreen"/> <asp:TreeNodeStyle ChildNodesPadding="5" Font-Bold="true" Font-Size="10pt"/> <asp:TreeNodeStyle ChildNodesPadding="5" Font-UnderLine="true" Font-Size="10pt"/> <asp:TreeNodeStyle ChildNodesPadding="10" Font-Size="8pt"/> </LevelStyles> <Nodes> <asp:TreeNode Text="Table of Contents" SelectAction="None"> <asp:TreeNode Text="Chapter One"> <asp:TreeNode Text="Section 1.0"> <asp:TreeNode Text="Topic 1.0.1"/> <asp:TreeNode Text="Topic 1.0.2"/> <asp:TreeNode Text="Topic 1.0.3"/> </asp:TreeNode> <asp:TreeNode Text="Section 1.1"> <asp:TreeNode Text="Topic 1.1.1"/> <asp:TreeNode Text="Topic 1.1.2"/> <asp:TreeNode Text="Topic 1.1.3"/> <asp:TreeNode Text="Topic 1.1.4"/> </asp:TreeNode> </asp:TreeNode> <asp:TreeNode Text="Chapter Two"> <asp:TreeNode Text="Section 2.0"> <asp:TreeNode Text="Topic 2.0.1"/> <asp:TreeNode Text="Topic 2.0.2"/> </asp:TreeNode> </asp:TreeNode> </asp:TreeNode> <asp:TreeNode Text="Appendix A" /> <asp:TreeNode Text="Appendix B" /> <asp:TreeNode Text="Appendix C" /> </Nodes> </asp:TreeView> <br /><br /> <asp:Button id="Submit" Text="Select Items" runat="server"/> <br /><br /> <asp:Label id="Message" runat="server"/> </form> </body> </html>
Available since 2.0